1. Field of the Invention
The present invention is directed to stringed musical instruments, and more particularly to stringed musical instruments with improved harmonic generation.
2. Description of the Related Art
An important characteristic of a musical instrument is its tone. A tone may be considered as a particular combination of a fundamental frequency and accompanying harmonics, each with a particular amplitude and phase. The combination of these harmonics gives an instrument its tone. For instance, an “A” note played on a violin will sound different from an “A” note played on a guitar, even though both “A” notes have a fundamental frequency of 440 Hz, because a violin has a different characteristic tone from a guitar. Likewise, a pure sine wave at 440 Hz, which has no accompanying harmonics, will sound different from an “A” played on either a violin or a guitar. Put simply, it is the harmonics accompanying each note that give an instrument its characteristic sound, or tone. In general, the more harmonics that accompany each note, the more complex the tone of the instrument, and the more pleasing the sound that is perceived by the listener.
The delicate purity of tone of the lute, viol and harp instruments found its zenith in quality in the twelfth and thirteenth centuries. The proportions of wood density and thickness of these instruments were of a much thinner and more responsive design than the later carved instruments. As venues graduated in size from the king's court and music rooms to theaters and concert halls, these designs evolved so as to accommodate higher string tension and acoustic cavity expansion, thereby producing a more powerful sound. Though these instruments seemed to perform well in the larger venues, the spectrum of tone and sustain was inhibited and shortened in proportion. In answer to this, the modern carved instrument evolved and was accepted, as it was found to recoup those lost qualities. Though drastically falling short of their predecessors, they none the less could be heard in the cheap seats. With very little change, these inadequacies are still present today.
Many of the stringed instruments, both antiquated and current, have several elements in common. The strings are fastened on the top side of the instrument, and generally extend along a neck. The tension of each string is adjustable at one or both ends, so that the instrument may be tuned. The strings acoustically couple to a soundboard through a bridge. In a closedbox instrument such as a guitar or violin, the soundboard or playing table may be domed or arched in places with respect to a coplanar edge, and may optionally have one or more holes in it that allow air to pass into and out of the instrument.
Another characteristic common to typical stringed instruments is that they inherently tend to produce too much energy in some harmonics, a condition which produces a type of dissonance known as “wolf tones.” Wolf tone arise from imperfections in the construction of musical instruments that cause unpleasant intonation. These imperfections tend to produce an eccentricity of resonance that is slightly sharp or slightly flat in relation to the principal note, which either enhances or damps the principal note to produce a characteristic fluttering or wailing sound. Wolf tones occur on many of the stringed instruments, but are most prevalent on the violin, viola, and violoncello.
Stringed instruments are corrected for wolf tones in various ways, both in the finished instrument as well as in the design of the instrument. Devices known as “wolf mutes” are available for finished instruments. One type of wolf mute mounts on the string between the bridge and the anchor. Another type is glued to the inside surface of the playing table. However, wolf mutes affect characteristics of the instrument, including loudness and timbre. In the design of the violin, the string length, bridge, tail piece, and saddle can all be adjusted to compensate for the inherent inharmonics so that the wolf tones are suppressed. In the guitar, the notes as determined by the placement of the frets, and example of which is set forth below in Table 1, is inharmonic to help suppress wolf tones. Note, for example, that the first harmonic of A 440 hertz is an inharmonic 847.3099 hertz, not the proper harmonic of 880 hertz.
TABLE 1A440Bb464.69551D578.13821F#719.27485B490.77708D#610.58688G759.64499C518.32251E644.85678G#802.28095C#547.41396F681.05012A847.30991
Unfortunately, the need to compensate for the inherent inharmonics of the stringed instrument compromises instrument performance.